1. Field of the Invention
This invention relates to a solar cell module, particularly to a two-side incidence type solar cell module capable of entering light from both front and rear surfaces provided with transparent front and rear surface members.
2. Description of Prior Art
Because solar light is unexhausted energy, a solar cell device for directly converting light energy into electrical energy has been developed as an energy source to substitute for environmentally harmful fossil fuels such as petroleum and coal. A plurality of solar cell elements are electrically connected in series or in parallel with each other to form a solar cell module and increase their output. The solar cell module can be used as a practical energy source.
A conventional solar cell module which generates power on one side surface is so structured that a plurality of solar cell elements 110 between a front surface glass 100 and a rear surface member 101 are sealed with a transparent and insulative resin 102 such as EVA (ethylene vinyl acetate).
The solar cell element 110 contains semiconductor material such as single crystalline silicon, polycrystalline silicon, or the like, and the solar cell elements 110 are connected in series by connection member 111 of a metal thin plate such as a copper foil plate or the like. The rear surface member 101 has a lamination film with a metal foil such as an aluminum (Al) foil or the like sandwiched with plastic films so that water entrance from a rear surface can be prevented.
The solar cell module is integrally formed by sandwiching the solar cell element 110 between the front surface glass 100 and the rear surface member 101 with a resin sheet of EVA or the like of 0.4-0.8 mm in thickness interposed and heating it at a reduced pressure.
On the other hand, a two-side incidence type solar cell element has been proposed, which is so structured that an electrode on a rear surface not only an electrode on a front light incidence side is a transparent electrode. With this structure, light is incident from both of the front and rear surfaces of the solar cell element. The rear surface of this solar cell element is formed of transparent material.
In the meantime, a solar cell module should be weather proof in order to withstand long-term use outside. The above conventional two-side incidence type structure uses transparent material for the rear surface member. When a transparent resin film is used as the rear surface member, water is likely to enter as compared with a lamination film with a metal foil sandwiched with plastic films. Therefore, it is necessary to take water penetration into consideration. Although a film of small water vapor transmission rate has been proposed as a transparent resin film, it still requires to be improved.
This invention was made to solve this problem and provides a solar cell module capable of improving reliability by improving moisture proofness.
Furthermore, this invention was made to improve reliability of the solar cell module by reducing water reaching to the front surface glass when the rear surface member is resin film and suppressing the sodium ions deposited from the front surface glass from reaching the front surface of the solar cell elements.
A solar cell module of this invention comprises a light transmitting member on a front surface side containing at least sodium, a rear surface resin film, a plurality of solar cell elements sealed with sealing resin between the light transmitting member on the front surface side and the rear surface resin film, and a water transmission preventing layer arranged in a position including at least an interval part between the solar cell elements adjacent each other.
The light transmitting member on the front surface side is glass and the rear surface resin film is a transparent resin film.
With the above structure, water entering though the rear surface resin film is blocked by the water transmission preventing layer and an increase of water contained in the sealing resin between the front surface glass and the solar cell elements can be prevented.
The water transmission preventing layer is formed of material with a smaller water vapor transmission rate than that of the sealing resin.
The material having a smaller water vapor transmission rate than that of the sealing resin can block water entering through the rear surface resin film.
The water transmission preventing layer is an inorganic oxide layer, a nitride layer, or a fluoride layer formed on a surface of the rear surface resin film.
The inorganic oxide layer, the nitride layer, or the fluoride layer has water barrier properties, and can function as the water transmission preventing layer.
The water transmission preventing layer is a thin plate glass bonded on a surface of the rear surface resin film.
The thin plate glass can prevent water transmission, and water entering through the rear surface resin film is blocked.
The water transmission preventing layer may be formed on a plane with the solar cell elements.
With this structure, water entering through the rear surface resin film is blocked by the solar cell elements and the water transmission preventing layer, and an increase of water contained in the sealing resin between the front surface glass and the solar cell elements.
The water transmission preventing layer may be formed so as to cover the interval part between the solar cell elements in the sealing resin.
With this structure, water entering through the rear surface resin film is blocked by the solar cell elements and the water transmission preventing layer, and an increase of water contained in the sealing resin between the front surface glass and the solar cell elements.
The water transmission preventing layer may be provided in a position corresponding to a position between the solar cell elements on an outer side of the rear surface resin film.
With the above structure, water entered though the rear surface resin film is blocked by the water transmission preventing layer and an increase of water contained in the sealing resin between the front surface glass and the solar cell elements.
The water transmission preventing layer is the rear surface resin film with the water vapor transmission rate not higher than 6.3 g/m2xc2x7day.
The resin film of water vapor transmission rate not higher than 6.3 g/m2xc2x7day can suppress water entrance, and an increase of water contained in the sealing resin between the front surface glass and the solar cell elements can be prevented.